A. Technical Field
The present invention pertains generally to document image processing; and relates more particularly to systems and methods for compensating for leakage related to double-sided document imaging.
B. Background
A common element of contemporary society is the handling of documents in physical and electronic forms. At times, it is more convenient or beneficial to work with documents in a physical form. And, at other times, such as for archiving, copying, transmitting, and the like, it is more convenient to have a physical document converted into an electronic image.
A physical document is printed on a substrate, typically paper. Because the document substrate has some degree of translucence or partial transparency, some of the image on the reverse side (verso) of the document is captured when imaging the front side (recto) of the document. The substrate translucence is particularly prevalent when the imaging of the document is performed using a scanner. When scanning, a bright light is used to illuminate the document, which tends to increase the translucence of the document. Thus, an image of the document generated by scanning results in the image containing information from both the recto and verso sides of the document. The appearance of portions of one side of the document being seen on the other side of the document is called “show-through” image information.
Another cause of the back-side image being partially visible on the front-side image is a result of ink seeping into, or even through, the paper. This phenomenon is typically referred to as “bleed-through.” However, improvements in printing and publishing have made the issue of bleed-through far less prevalent and is typically associated with old documents. Both “show-through” and “bleed-through” shall be treated as “leakage,” meaning that at least a portion of a back-side image affects the front-side image when duplicating the front-side image.
Various attempts have been used to mitigate leakage effects when imaging a document. For example, the show-through problem can be reduced by placing a black backing behind the document being imaged. That way, light that passes through the document substrate is absorbed by the backing and is not reflected back to the imaging sensors. Such a method, however, has limitations. First, some of the light reflects off the back-side image and affects the imaging of the front-side. Second, some duplex scanning devices, particularly those used for high volume scanning, scan both images at the same time, making it impossible to have a black backing. Finally, the black backing itself can create a show-through effect in the resultant image.
Accordingly, what is needed are systems and methods that can mitigate the effects of leakage of a back-side image of a document into an image taken of the front-side of the document.